Phenology and Response of Clipping in Relation to Invasiveness of Parthenium Hysterophorus L.
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Department of Botany
Abstract
Phenology of parthenium weed ( Parthenium hysterophorus L.) was monitored for a year
from May 2011 to April 2012 in Sundarighat, Kirtipur of Kathmandu district, Central
Nepal. In permanently marked plots, different parameters such as maximum height,
density and number of seedling cohort produced were noted assuming that they might
have critical role in determining the invasiveness of this weed. The study also focused on
the response of this weed to clipping (mechanical damage) in terms of seed output, height
and number of branches produced. To meet the objectives of the study, two approaches,
field sampling and the clipping experiment were applied in green house. In field sampling
a total of eight transects (1 m × 10 m) in pair, each transect having five plots (1 m × 1 m)
selected randomly were sampled. In each plot, number of vascular plant species present
and number of individuals of parthenium seedling, juvenile and flowering individuals and
their maximum height were recorded every month for a year. In clipping experiment, out
of 60, 15 plants were selected randomly as a control and remaining 45 were subjected to
single, double and triple clipping. At last, seeds were harvested separately for each
treatment and the maximum height and number of branches produced were recorded for
each plant. There was no significant difference among the seedling density in rainy, fall
and summer seasons. The four cohorts of seedlings emerged in the study site in a year.
The highest seedling density was recorded in February. Whereas, density of reproductive
individual showed significant difference between rainy and fall seasons but no significant
difference between winter and summer seasons. Flowering was observed in 8 out of 12
months showing peak in July. The vascular plant species richness did not show any
relationship with parthenium density but it showed negative relation with the height in
July which was the month with highest height. The significant difference was obtained in
seed output and mean height among control, single clipping, double clipping and triple
clipping. Number of branches increased with increasing clipping frequency. This weed
did not compensate in seed production and growth following repeated clippings. It can be
concluded that prolonged period of flowering and production of several cohort of
seedling could be the contributing factor for high invasiveness of parthenium.
Keywords: Management, Plant species richness, Seedling cohort, Kathmandu.